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冲压模具毕业设计1.绪论1.1冲压的概念、特点及应用冲压是利用安装在冲压设备(主要是压力机)上的模具对材料施加压力,使其产生分离或塑性变形,从而获得所需零件(俗称冲压或冲压件)的一种压力加工方法。冲压通常是在常温下对材料进行冷变形加工,且主要采用板料来加工成所需零件,所以也叫冷冲压或板料冲压。冲压是材料压力加工或塑性加工的主要方法之一,隶属于材料成型工程术。冲压所使用的模具称为冲压模具,简称冲模。冲模是将材料(金属或非金属)批量加工成所需冲件的专用工具。冲模在冲压中至关重要,没有符合要求的冲模,批量冲压生产就难以进行;没有先进的冲模,先进的冲压工艺就无法实现。冲压工艺与模具、冲压设备和冲压材料构成冲压加工的三要素,只有它们相互结合才能得出冲压件。 与机械加工及塑性加工的其它方法相比,冲压加工无论在技术方面还是经济方面都具有许多独特的优点。主要表现如下。(1) 冲压加工的生产效率高,且操作方便,易于实现机械化与自动化。这是因为冲压是依靠冲模和冲压设备来完成加工,普通压力机的行程次数为每分钟可达几十次,高速压力要每分钟可达数百次甚至千次以上,而且每次冲压行程就可能得到一个冲件。(2)冲压时由于模具保证了冲压件的尺寸与形状精度,且一般不破坏冲压件的表面质量,而模具的寿命一般较长,所以冲压的质量稳定,互换性好,具有“一模一样”的特征。(3)冲压可加工出尺寸范围较大、形状较复杂的零件,如小到钟表的秒表,大到汽车纵梁、覆盖件等,加上冲压时材料的冷变形硬化效应,冲压的强度和刚度均较高。(4)冲压一般没有切屑碎料生成,材料的消耗较少,且不需其它加热设备,因而是一种省料,节能的加工方法,冲压件的成本较低。但是,冲压加工所使用的模具一般具有专用性,有时一个复杂零件需要数套模具才能加工成形,且模具 制造的精度高,技术要求高,是技术密集形产品。所以,只有在冲压件生产批量较大的情况下,冲压加工的优点才能充分体现,从而获得较好的经济效益。 冲压地、在现代工业生产中,尤其是大批量生产中应用十分广泛。相当多的工业部门越来越多地采用冲压法加工产品零部件,如汽车、农机、仪器、仪表、电子、航空、航天、家电及轻工等行业。在这些工业部门中,冲压件所占的比重都相当的大,少则60%以上,多则90%以上。不少过去用锻造=铸造和切削加工方法制造的零件,现在大多数也被质量轻、刚度好的冲压件所代替。因此可以说,如果生产中不谅采用冲压工艺,许多工业部门要提高生产效率和产品质量、降低生产成本、快速进行产品更新换代等都是难以实现 的。1.2 冲压的基本工序及模具 由于冲压加工的零件种类繁多,各类零件的形状、尺寸和精度要求又各不相同,因而生产中采用的冲压工艺方法也是多种多样的。概括起来,可分为分离工序和成形工序两大类;分离工序是指使坯料沿一定的轮廓线分离而获得一定形状、尺寸和断面质量的冲压(俗称冲裁件)的工序;成形工序是指使坯料在不破裂的条件下产生塑性变形而获得一定形状和尺寸的冲压件的工序。 上述两类工序,按基本变形方式不同又可分为冲裁、弯曲、拉深和成形四种基本工序,每种基本工序还包含有多种单一工序。 在实际生产中,当冲压件的生产批量较大、尺寸较少而公差要求较小时,若用分散的单一工序来冲压是不经济甚至难于达到要求。这时在工艺上多采用集中的方案,即把两种或两种以上的单一工序集中在一副模具内完成,称为组合的方法不同,又可将其分为复合-级进和复合-级进三种组合方式。 复合冲压在压力机的一次工作行程中,在模具的同一工位上同时完成两种或两种以上不同单一工序的一种组合方法式。 级进冲压在压力机上的一次工作行程中,按照一定的顺序在同一模具的不同工位上完面两种或两种以上不同单一工序的一种组合方式。 复合-级进在一副冲模上包含复合和级进两种方式的组合工序。 冲模的结构类型也很多。通常按工序性质可分为冲裁模、弯曲模、拉深模和成形模等;按工序的组合方式可分为单工序模、复合模和级进模等。但不论何种类型的冲模,都可看成是由上模和下模两部分组成,上模被固定在压力机工作台或垫板上,是冲模的固定部分。工作时,坯料在下模面上通过定位零件定位,压力机滑块带动上模下压,在模具工作零件(即凸模、凹模)的作用下坯料便产生分离或塑性变形,从而获得所需形状与尺寸的冲件。上模回升时,模具的卸料与出件装置将冲件或废料从凸、凹模上卸下或推、顶出来,以便进行下一次冲压循环。1.3 冲压技术的现状及发展方向 随着科学技术的不断进步和工业生产的迅速发展,许多新技术、新工艺、新设备、新材料不断涌现,因而促进了冲压技术的不断革新和发展。其主要表现和发展方向如下。(1).冲压成形理论及冲压工艺方面 冲压成形理论的研究是提高冲压技术的基础。目前,国内外对冲压成形理论的研究非常重视,在材料冲压性能研究、冲压成形过程应力应变分析、板料变形规律研究及坯料与模具之间的相互作用研究等方面均取得了较大的进展。特别是随着计算机技术的飞跃发展和塑性变形理论的进一步完善,近年来国内外已开始应用塑性成形过程的计算机模拟技术,即利用有限元(FEM)等有值分析方法模拟金属的塑性成形过程,根据分析结果,设计人员可预测某一工艺方案成形的可行性及可能出现的质量问题,并通过在计算机上选择修改相关参数,可实现工艺及模具的优化设计。这样既节省了昂贵的试模费用,也缩短了制模具周期。 研究推广能提高生产率及产品质量、降低成本和扩大冲压工艺应用范围的各种压新工艺,也是冲压技术的发展方向之一。目前,国内外相继涌现出精密冲压工艺、软模成形工艺、高能高速成形工艺及无模多点成形工艺等精密、高效、经济的冲压新工艺。其中,精密冲裁是提高冲裁件质量的有效方法,它扩大了冲压加工范围,目前精密冲裁加工零件的厚度可达25mm,精度可达IT1617级;用液体、橡胶、聚氨酯等作柔性凸模或凹模的软模成形工艺,能加工出用普通加工方法难以加工的材料和复杂形状的零件,在特定生产条件下具有明显的经济效果;采用爆炸等高能效成形方法对于加工各种尺寸在、形状复杂、批量小、强度高和精度要求较高的板料零件,具有很重要的实用意义;利用金属材料的超塑性进行超塑成形,可以用一次成形代替多道普通的冲压成形工序,这对于加工形状复杂和大型板料零件具有突出的优越性;无模多点成形工序是用高度可调的凸模群体代替传统模具进行板料曲面成形的一种先进技术,我国已自主设计制造了具有国际领先水平的无模多点成形设备,解决了多点压机成形法,从而可随意改变变形路径与受力状态,提高了材料的成形极限,同时利用反复成形技术可消除材料内残余应力,实现无回弹成形。无模多点成形系统以CAD/CAM/CAE技术为主要手段,能快速经济地实现三维曲面的自动化成形。(2.)冲模是实现冲压生产的基本条件.在冲模的设计制造上,目前正朝着以下两方面发展:一方面,为了适应高速、自动、精密、安全等大批量现代生产的需要,冲模正向高效率、高精度、高寿命及多工位、多功能方向发展,与此相比适应的新型模具材料及其热处理技术,各种高效、精密、数控自动化的模具加工机床和检测设备以及模具CAD/CAM技术也在迅速发展;另一方面,为了适应产品更新换代和试制或小批量生产的需要,锌基合金冲模、聚氨酯橡胶冲模、薄板冲模、钢带冲模、组合冲模等各种简易冲模及其制造技术也得到了迅速发展。 精密、高效的多工位及多功能级进模和大型复杂的汽车覆盖件冲模代表了现代冲模的技术水平。目前,50个工位以上的级进模进距精度可达到2微米,多功能级进模不仅可以完成冲压全过程,还可完成焊接、装配等工序。我国已能自行设计制造出达到国际水平的精度达25微米,进距精度23微米,总寿命达1亿次。我国主要汽车模具企业,已能生产成套轿车覆盖件模具,在设计制造方法、手段方面已基本达到了国际水平,但在制造方法手段方面已基本达到了国际水平,模具结构、功能方面也接近国际水平,但在制造质量、精度、制造周期和成本方面与国外相比还存在一定差距。 模具制造技术现代化是模具工业发展的基础。计算机技术、信息技术、自动化技术等先进技术正在不断向传统制造技术渗透、交叉、融合形成了现代模具制造技术。其中高速铣削加工、电火花铣削加工、慢走丝切割加工、精密磨削及抛光技术、数控测量等代表了现代冲模制造的技术水平。高速铣削加工不但具有加工速度高以及良好的加工精度和表面质量(主轴转速一般为1500040000r/min),加工精度一般可达10微米,最好的表面粗糙度Ra1微米),而且与传统切削加工相比具有温升低(工件只升高3摄氏度)、切削力小,因而可加工热敏材料和刚性差的零件,合理选择刀具和切削用量还可实现硬材料(60HRC)加工;电火花铣削加工(又称电火花创成加工)是以高速旋转的简单管状电极作三维或二维轮廓加工(像数控铣一样),因此不再需要制造昂贵的成形电极,如日本三菱公司生产的EDSCAN8E电火花铣削加工机床,配置有电极损耗自动补偿系统、CAD/CAM集成系统、在线自动测量系统和动态仿真系统,体现了当今电火花加工机床的技术水平;慢走丝线切割技术的发展水平已相当高,功能也相当完善,自动化程度已达到无人看管运行的程度,目前切割速度已达到300mm/min,加工精度可达1.5微米,表面粗糙度达Ra=010.2微米;精度磨削及抛光已开始使用数控成形磨床、数控光学曲线磨床、数控连续轨迹坐标磨床及自动抛光等先进设备和技术;模具加工过程中的检测技术也取得了很大的发展,现在三坐标测量机除了能高精度地测量复杂曲面的数据外,其良好的温度补偿装置、可靠的抗振保护能力、严密的除尘措施及简单操作步骤,使得现场自动化检测成为可能。此外,激光快速成形技术(RPM)与树脂浇注技术在快速经济制模技术中得到了成功的应用。利用RPM技术快速成形三维原型后,通过陶瓷精铸、电弧涂喷、消失模、熔模等技术可快速制造各种成形模。如清华大学开发研制的“M-RPMS-型多功能快速原型制造系统”是我国自主知识产权的世界惟一拥有两种快速成形工艺(分层实体制造SSM和熔融挤压成形MEM)的系统,它基于“模块化技术集成”之概念而设计和制造,具有较好的价格性能比。一汽模具制造公司在以CAD/CAM加工的主模型为基础,采用瑞士汽巴精化的高强度树脂浇注成形的树脂冲模应用在国产轿车试制和小批量生产开辟了新的途径。(3) 冲压设备和冲压生产自动化方面 性能良好的冲压设备是提高冲压生产技术水平的基本条件,高精度、高寿命、高效率的冲模需要高精度、高自动化的冲压设备相匹配。为了满足大批量高速生产的需要,目前冲压设备也由单工位、单功能、低速压力机朝着多工位、多功能、高速和数控方向发展,加之机械乃至机器人的大量使用,使冲压生产效率得到大幅度提高,各式各样的冲压自动线和高速自动压力机纷纷投入使用。如在数控四边折弯机中送入板料毛坯后,在计算机程序控制下便可依次完成四边弯曲,从而大幅度提高精度和生产率;在高速自动压力机上冲压电机定转子冲片时,一分钟可冲几百片,并能自动叠成定、转子铁芯,生产效率比普通压力机提高几十倍,材料利用率高达97%;公称压力为250KN的高速压力机的滑块行程次数已达2000次/min以上。在多功能压力机方面,日本田公司生产的2000KN“冲压中心”采用CNC控制,只需5min时间就可完成自动换模、换料和调整工艺参数等工作;美国惠特尼公司生产的CNC金属板材加工中心,在相同的时间内,加工冲压件的数量为普通压力机的410倍,并能进行冲孔、分段冲裁、弯曲和拉深等多种作业。 近年来,为了适应市场的激烈竞争,对产品质量的要求越来越高,且其更新换代的周期大为缩短。冲压生产为适应这一新的要求,开发了多种适合不同批量生产的工艺、设备和模具。其中,无需设计专用模具、性能先进的转塔数控多工位压力机、激光切割和成形机、CNC万能折弯机等新设备已投入使用。特别是近几年来在国外已经发展起来、国内亦开始使用的冲压柔性制造单元(FMC)和冲压柔性制造系统(FMS)代表了冲压生产新的发展趋势。FMS系统以数控冲压设备为主体,包括板料、模具、冲压件分类存放系统、自动上料与下料系统,生产过程完全由计算机控制,车间实现24小时无人控制生产。同时,根据不同使用要求,可以完成各种冲压工序,甚至焊接、装配等工序,更换新产品方便迅速,冲压件精度也高。(4)冲压标准化及专业化生产方面 模具的标准化及专业化生产,已得到模具行业和广泛重视。因为冲模属单件小批量生产,冲模零件既具的一定的复杂性和精密性,又具有一定的结构典型性。因此,只有实现了冲模的标准化,才能使冲模和冲模零件的生产实现专业化、商品化,从而降低模具的成本,提高模具的质量和缩短制造周期。目前,国外先进工业国家模具标准化生产程度已达70%80%,模具厂只需设计制造工作零件,大部分模具零件均从标准件厂购买,使生产率大幅度提高。模具制造厂专业化程度越不定期越高,分工越来越细,如目前有模架厂、顶杆厂、热处理厂等,甚至某些模具厂仅专业化制造某类产品的冲裁模或弯曲模,这样更有利于制造水平的提高和制造周期的缩短。我国冲模标准化与专业化生产近年来也有较大发展,除反映在标准件专业化生产厂家有较多增加外,标准件品种也有扩展,精度亦有提高。但总体情况还满足不了模具工业发展的要求,主要体现在标准化程度还不高(一般在40%以下),标准件的品种和规格较少,大多数标准件厂家未形成规模化生产,标准件质量也还存在较多问题。另外,标准件生产的销售、供货、服务等都还有待于进一步提高。 盖冒垫片设计说明书一、工件工艺性分析如右图1所示:工件为有凸缘圆筒形零件,且在凸缘上均匀分布4个相同的孔。故可得知此工件为:落料拉深冲孔所得,其加工工艺过程为:落料拉深冲孔,各尺寸关系如图1所示一、 拉深工艺及拉深模有设计1、 设计要点设计确定拉深模结构时为充分保证制件的质量及尺寸的精度,应注意以下几点1) 拉深高度应计算准确,且在模具结构上要留有安全余量,以便工件稍高时仍能适应。2) 拉深凸模上必须设有出气孔,并注意出气孔不能被工件包住而失去作用。3) 有凸缘拉深件的高度取决胜于上模行程,模具中要设计有限程器,以便于模具调整。4) 对称工件的模架要明显不对称,以防止上、下模位置装错,非旋转工件的凸、凹模装配位置必须准确可行,发防松动后发生旋转,偏移而影响工件质量,甚至损坏模具。5) 对于形状复杂,需经过多次拉深的零件,需先做拉深模,经试压确定合适的毛坯形状和尺寸后再做落料模,并在拉深模上按已定形的毛坯,设计安装定位装置。6) 弹性压料设备必须有限位器,防止压料力过大。7) 模具结构及材料要和制件批量相适应。8) 模架和模具零件,要尽是使用标准化。9) 放入和取出工件,必须方便安全。2、 有凸缘圆筒形件的拉深方法及工艺计算有凸缘筒形件的拉深原理与一般圆筒形件是相同的,但由于带有凸缘,其拉深方法及计算方法与一般圆筒形件有一定差别。1) 在凸缘拉深件可以看成是一般圆筒形件在拉深未结束时的半成品,即只将毛坯外径拉深到等于法兰边(即凸缘)直径df时的拉深过程就结束。因此其变形区的压力状态和变形特点应与圆筒形件相同。 根据凸缘的相对直径df/d比值同有凸缘筒形件可分为:窄凸缘筒形件(df/d=1.11.4)和宽凸缘筒形件(df/d1.4)。显然此工件df/d=50/21=2.381.4为宽凸缘筒形件。下面着重对宽凸缘件的拉深进行分析,主要介绍其与直壁筒形件的不同点。当rp=rd=r时(图2),宽凸缘件毛坯直径的计算公式为:(1)根据拉深系数的定义宽凸缘件总拉深系数仍可表示为:(2)3、 宽凸缘圆筒形件的工艺计算要点1)毛坯尺寸的计算,毛坯尺寸的计算仍按等面积原理进行,参考无凸缘筒形件毛坯的计算方法计算,毛坯直径的计算公式见式(1),其中df要考虑修边余量,其值可从冲压工艺与模具设计表4.22中查得1.6mm即df=50+1.6=51.6mm则D=54.75mm根据拉深系数的定义,宽凸缘件总拉深系数仍可表示为:M=2)判断工件是否一次拉成,这只须比较工件实际所需的总拉深系数和h/d与凸缘件第一次拉深系数和极限拉深系数的相对高度即可。m总m1,当1,h/dh1/d1时可以一次拉成,工序计算到此结束,否则应进行多次拉深。m总=0.38 h/d=0.33。由冲压工艺与模具设计表4.2.6查得此凸缘件的第一次拉深系数m1=0.37。由表4.2.7查得此凸缘件的第一次拉深最大相对高度h1/d1=0.280.35之间,可知m总m1,h/dh1/d1可一次拉成。4、拉深凸模和凹模的间隙拉深模间隙是指单面间隙,间隙的大小对拉深力,拉深件的质量,拉深模的寿命都有影响,若c值大小,凸缘区变厚的材料通过间隙时,校正和变形的阻力增加,与模具表面间的摩擦,磨损严重,使拉深力增加,需件变薄严重,甚至拉破,模具寿命降低。间隙小时得到的零件侧壁平直而光滑,质量较好,精度较高。间隙过大时,对毛坯的校直和挤压作用减小,拉深力降低,模具的寿命提高,但零件的质量变差,冲出的零件侧壁不直。因此拉深模的间隙值也应合适,确定c时要考虑压边状况,拉深次数和工件精度高。其原则是:即要考虑材料本身的公差,又要考虑板料的增厚现象,间隙一般都比毛坯厚度略大一些。不用压边圈时,考虑到起皱的可能性取间隙值为:C=(11.1)tmax有压边圈时,间隙数值也可按表4.6.3取值(冲压工艺与模具设计),此工件的拉深间隙可取,C=1.1t=1.1mm4、拉深凸模,凹模的尺寸及公差工件的尺寸精度由末次拉深的凸、凹模的尺寸及公差决定,因此除最后一道拉深模的尺寸公差需要考虑外,首次及中间各道次的模具尺寸公差和拉深半成品的尺寸公差没有必要做严格限制。这是模具的尺寸只取等于毛坯的过渡尺寸即可。此工件内形尺寸公差有要求,故以凸模为基准,先定凸模尺寸考虑到凸模基本不磨损,(其尺寸关系如图3所示)以及工件的回弹情况,凸模开始尺寸不要取得过大。其值为:Dp=(d+0.4)-p凸模尺寸为:Dd=(d+0.4+2C)+ d凸、凹模的制造公差p和d可根据工件的公差来选定。工件公差为TT13级以上时p和d可按TT68级取,工件公差在IT14级以下时,则p和d可按IT10级取:Dp=(20+0.40.2)0-0.021=20.080-0.021mmDd=(d+0.4+2c)0+d =(20+0.40.2+21.1)0+d=22.280+0.021mm5、凹模圆角半径rd拉深时,材料在经过凹模圆角时不仅因为发生弯曲变形需要克服弯曲阻力,还要克服因相对流动引起的磨檫阻力,所以rd大小对拉伸工件的影响非常大。主要有以下影响:1)拉伸力的大小;2)拉伸件的质量;3)拉伸模的寿命。rd小时材料对凹模的压力增加,磨檫力增大,磨损加剧,使磨具的寿命降低。所以rd的值即不能太大,也不能太小。在生产上一般应尽量避免采用过小圆角半径,在保证工件质量的前提下尽量取大值,以满足模具寿命要求。通常可按经验公式计算:rd=式中D为毛坯直径或上道工序拉深件直径;d为本道拉深后的直径rd应大于或等于2t,若其值小于2t,一般很难拉出,只能靠拉深后整形得到所需零件,故可取rd=2.5mm6、凸模圆角半径rp凸模圆角半径对拉深工序的影响没有凹模圆角半径大,但其值也必须合格,一般首次拉深时凸模圆角半径为rp=(0.71.0)rd这里取rp =1.0rd=2.5mm三、冲裁工艺及冲裁模具的设计1、凸模与凹模刃口尺寸的计算冲裁件的尺寸精度主要决定于模具刃口的尺寸精度。模具的合理间隙也要靠模具刃口尺寸制造精度来保证。正确确定模具刃口尺寸及其制造公差,是设计冲裁模的主要任务之一。从生产实践可发现:由于凸凹模之间存在间隙,使落下的料或伸出的孔却带有锥度,且落料件的大端尺寸等于凹模尺寸,冲孔件的小端尺寸等于凸模尺寸;在测量于使用中,落料件以大端尺寸为基准,冲孔件以小端尺寸为基准。2、凸、凹模刃口尺寸的计算方法由于加工模具的方法不同,凸模与凹模刃口部分尺寸的计算公式与制造公差的标注也不同,刃口尺寸的计算方法可分为以下两种情况:凹模与凸模分开加工,凸模和凹模配合加工,从此工件的结构上分析,选择凸模与凹模分开加工的制造方法:采用这种方法,凸模和凹模分别按图纸加工至尺寸,要分别标注凸模和凹模的刃口尺寸及制造公差(凸模p、凹模d),适用于圆形或简单形状的制件。为了保证初始间隙值小于最大合理间隙2Cmax,必须满足下列条件:或取: 也就是说,新制造模具应该是,否则制造的模具部隙已超过允许变动范围2Cmin2Cmax,影响模具的使作寿命。下面对落料和冲孔两咱情况分别进行讨论。1) 落料高工件的尺寸为D-0,根据计算原则,落料时以凹模为设计基准。首先确定凹模尺寸,凹模的基本尺寸接近或等于制件轮廓的最小极限尺寸,再减小凸模尺寸以保证最小合理间隙值2Cmin。名部分分配位置如图5(a)所示。其计算公式如下(3) (4)代入数据得校核;由此可知,只有缩小、,提高制造精度,才保证间隙在合理范围内,此时可取、,放得:2)冲孔设冲孔尺寸为,根居以上原则,冲孔时以凸模设计为基准,首先确定凸模刃口尺寸,使凸模基本尺寸接近或等于工件孔的最大极限尺寸,再增大凹模尺寸,凸模制造偏差为负偏差,凹模取正偏差,名部分分配位置如图5.b所示,其计算公式如下:在同一工步制件上冲出两个以上孔时,凹模型孔中心距Ld按下式确定:代入数据校核孔距尺寸: 3)凹模洞的类形常用凹模洞口的类形如图6所示: 图 6其中图a、b、c为直筒式刃的凹模,其特点是制造方便,刃口强度高,刃磨后工作部分尺寸不变,广泛用于冲裁公差要求较小,形状复杂的精密制件。但因废料(或制件的聚集而增大了推件力和凹模的胀裂力,给凸、凹模的强度都带来了不利的影响。一般复合模上出件的冲裁模用图a、c型,下出件的冲裁模用图b或图a型,图d、e型是锥筒式刃口,在凹模内不聚集材料,侧壁磨损小,但刃口强度差,刃磨后刃口径向尺寸略有增大(如300时,刃磨0.1mm时,其尺寸增大0.0017mm凹模锥角,后角和洞高度h,均随制件材料厚度增加而增大,一般取15302030 h=4-10mm综上所述及其对工件孔分析,选择B型凹模洞口,取h=6mm204)凹模的外形尺寸凹模的外形一般有矩形与圆形两种。凹模的外形尺寸应保证凹模有足够的强度,刚度和修磨量,凹模的外形尺寸一般是根据被冲材料的厚度和冲裁件的最大外形尺寸来确定的如图7所示凹模的厚度为:1+ kb (15)凹模壁厚度为c=(1.52)H (3040mm)式中b为冲裁件的最大外形尺寸;K为系数,是考虑板料厚度影响的系数可以冲压工艺与模具设计表282中查得代入数据可得冲孔凹模 H=15mm c=30mm落料凹模H=0.3554.75=20mm c=40mm四、模具的其它零件1、模具除简单冲模外,一般冲模多利用模架的结构。模架的和种类很多,要根据模具的精度要求,模具的类别,模具的大小选择合适的模架.模架的选择可从实用模具技术手册P192页选择标准架。根据查阅的内容及分析,此复合模可选用后侧导柱模架导、导柱安装在后侧,有偏心裁荷时容易歪斜,滑动不够平稳,可从左右前三个方向关料操作比较方便。常用于一般要求的小型工件的冲裁和拉深模。所选模架的结构及尺寸关系如图8所示:L =250mm B=160mm 上模座:25016045 下模座25016050导柱,32190 导套 3210543 Hmax=210 Hmin=170mm 其余尺寸见上下模座零件图,可以冲压手册冲压模具常用标准件选择。2模柄模柄有多种形式,要根据模具的结构特点,选用模柄的形式模柄的直径根据所选压力机的模柄孔径确定,模柄可根据实用模具技术手册P201页选择,经查阅各种 模柄的特点,选用压入式模柄,这种模柄应用比较广泛压入模柄的结构和尺寸,可参表11-10制造,表中B型模柄中间有孔可按装打料杆,用压力机的打料模杆进行打料,模柄的结构及尺寸关系如图9所示。 图 9d=30D=32D1=42mmh=78mmh2=30mmh1=5mmb=2mma=0.5mmd1(H7)=6+0.0120d2=11mm3、卸料板卸料板的主要作用是将冲压的料从凸模或凸、凹模上推下来,此外在进模比较复杂的模具中,卸料板还具有保护小凸模作用,常用的卸料板结构形式及适用范围见表11-24和第八章级进模表8-10实用模具技术手册卸料板的尺寸可根据实用模具技术手册表11-25查得,本模具选用弹压式卸料板。卸料板的结构与尺寸关系如图10所示,ho=16mmB=150mmC=(0.10.2)t=0.2mm)4弹顶和推出装置弹顶装置由弹簧元件组成装于模具的下面通过顶杆起到推料的作用,弹顶装置通常在压力机的工作台孔中,弹顶装置结构形式见表11-26实用模具技术手册,具体结构及尺寸见装配图及零件图所示,见图表(10)设计模具时选用标准的弹簧。已知冲裁时卸料为 FQ=3.8 可选圆钢丝螺压缩弹簧,由表11-28查得d=8.0mm D2=50mm F=1990N. Dmax=38mmDmin=62mm; 节距P=14.9mm5、导向装置(导柱 导套)导向装置指得是模架上的导柱、导套。模具在开模,闭模过程中,导柱和导套起导向的作用,使得凸凹模正确的闭合,故此,导柱、导套需要有严格的配合精度及尺寸要求,导柱、导套的选择可以冲压手册中选取,(取H7/h6配合)如图11 a导柱的具体尺寸为:d=32 L=190mm导套的具体尺寸为(图11 .b) 图11D=32D(r6)=45L=105mmh=43mmL=25mm油槽数为2b=3;a=16、固定零件(固定板、垫板)1)垫板的作用是承受凸模和凹模的压力,防止过大的冲压,在上下模座上压出凹坑,影响模具的正常工作,垫板厚度根据压力机的大小选择,一般取5-12mm,外形与固定板相同,材料45钢,热处理后硬度为45-48HRC,如图12a .b所示:垫板在模具中的受力情况2)固定板 固定板的作用起固定凸、凹模,防止其在冲压过程中松动,造成模具的损坏,固定板的形状要根据凸、凹模而定,而外形尺寸与垫板相似。固定板和具体形状尺寸见零件图所示。7、连接零件此类零件包括螺钉、销钉等,主要作用是联接其它零部伯,使之共同完成工件的制造,螺钉和销钉可由冲压手册第十章、第七、八章查选,形状及尺寸见七、八节图所示现选螺钉M12 圆柱销 d=8,则冲压模上有关螺钉孔的尺寸见表10-28冲压手册D=27 d=17.5卸料螺钉选M16,具体尺寸见表10-29冲压手册五、压力机的选择压力机的选择要考虑,冲裁力、拉深力以及卸料力、推件力、顶件力,压力机的总吨位应大于等以上所有力之和1.3倍,普通刃冲裁模,其冲裁力FP一般可按下式计算。FP= KPtL式中为材料的抗剪强度,L为冲裁周边总长(mm),t为材料厚度,系数KP是考虑到冲裁模刃口的磨损,凸模与凹模间隙的波动(数值的变化或分布不均匀)润滑情况,材料力学性能与厚度公差的变化等因素而设置的安全系数,一般取1.3,当查不到强度时,可用强度,b代替,而取KP=1的近似计算法计算,材料钢的强度可以冲压工艺与模具设计表1.4.1查得=260MPa360MPa。 现取=340MPaFP1=1.313.1454.75340=76KNFP2=1.313.145340=7KN影响卸料力、推料力和顶件力的因素很多,要精确的计算出很困难,在实际生产采用经验公式计算:卸料力:FQ=KFp 推料力:FQ1=nK1Fp顶件力:FQ2=K2Fp式中: 卸料力系数,其值为 0.020.06 (薄料取大值,厚料取小值)推件力系数,其值为0.030.07 (薄料取大值,厚料取小值) 顶件力系数,其值为0.040.08 (薄料取大值,厚料取小值) n为梗塞在凹模内的制件或废料数量,n=h/t,h为直刃口部分的高,t为材料的厚度,h取410mm , 现取h=6mm 本模具中只有卸料力和推件力即可则:FQ=0.0576=3.8KN FQ1=6/10.067=2.52KN2)拉深力理论计算拉深力可以推导,但它使用不便,生产中常利用经验公式计算拉深力,第次拉深(一次拉深成形时)F1=d1tbk1式中b为材料的抗拉强度,K1为系数,查表4.5.4(冲压工艺与模具设计)代入数据可得F1=3.142113901=25.7KN压边力:FQ=0.2525.7=6.4KM卸料力: FQ=KF=0.0425.7=1.02KN综上所述:F总=76+7+3.8+2.25+25.7+6.4+1.02=123KNF压力=1.3 F总=1.3123=160 KN由实用模具技术手册P22页,应用压力机的选择查表2-3可选择J2316型压力机,其参数可参考表23六、 主要组件的装配1模柄的装配,因为所示模具的模柄是从以上模座的下而向上压入的,所以在安装凸模固定板和垫板之前,应先把模柄装好。模柄与上模座的配合要求是H7/m6.装配时,先在压力机上将模柄压入,再加工定俭销孔或螺纹孔。然后把模柄端面突出部分锉平或磨平,安装好模柄后,用角尺检查模柄与上模座上平面的垂有度。2、凸模和装配,凸模与固定板的配合要求为H7/m6.。装配时,先在压力机上将凸模固定板内,检查凸模的垂直度,然后将固定板的上平面与凸模尾部一起磨平,为了保持凸模刀口锋利还应将凸模的端面磨平。3、弹压卸料板的装配,弹压卸料板起压料和卸料的作用。装配的保证它与凸模之间具有适当的间隙,其装配方法是,将弹压卸料板 装入固定板的凸模内,在固定板与卸料板之间垫上平行垫块,并用平等夹板将它们夹紧,然后按卸料板上的螺孔在固定板上抽窝,拆开后钻固定板上的螺钉穿过孔。4、模架的技术要求及装配组成模架的各零件均应符合相应的技术条件,其中特别重要的是每对导柱,导套的配合间隙应符合要求。装配成套的模架,多项技术指标(上模座上平面对下模座下平面的平行度)导柱轴心线对下模座下平面的垂直度和导套孔轴心线对上模座下面垂直度)应符合相应精度等级要求。装配后的模架,上模座沿导柱上、下移动平稳无阻滞现象,压入上、下模座的导柱导柱离其它装表面应有12mm距离,压入后就牢固。装配成套的模架,各零件的工作表不应有碰伤,裂 以及其它机械损伤模架的装配主要指导柱导套的装配,目前大多数导柱,导套与模座之间采用过盈配合,但也有少数采用粘 工艺的,即将上下模座孔扩大,降低其加工要求,同时将导柱、导套之间冷入粘结剂,即可使用导柱,导套固定,滑动导向模架常用的装配工艺和检验方法有压入导套、压入导套安、装导套。七、模具的工作过程 本模具是一套倒装的落料拉深冲孔的复合模。前后送料,挡料销19限位,导向销20导正。上模下行凸凹模11与拉深凹模18接触进行拉深,工件成型后,上模上行,打杆1推动打板12把工件从凸凹模11中打出。落料废料有弹簧8推动卸料板10推出。体会俗话说“凡事必亲躬”,唯有自己亲自去做的事,才懂得其过程的艰辛。通过做这次大作业,我着实遇到了不少的困难,构思、定数据、画图、写论文等都得自己去做。每天泡在图书馆,找例证、查资料,个中自有不少困难,而这些难题都是课本中所不曾提到过的。开始时,由于书本上没有任何提示,我甚至不知道从何入手,只能与同学们相互切磋,这样我慢慢地入了门,进而也可以自己搞定了。这其中有一个习惯问题最需要克服。众所周知,课堂、书本给我们的都是一种确切的数据,但实际上你去做的时候就会发现它们都是经验性的,也就是说需要你根据从资料上查得的范围靠经验自己去定,这就给习惯于接受确切数字的我带来了很大的挑战。幸而,最终我还是学会了怎样去查找自己想要的资料,这应该是这次作业的一大收获吧。第二大收获就是学会了做一次设计项目的具体流程。从策划构思、总体设计到各个模块的的具体设计及其组合,再到编写需要提交的论文,这一切如今仍历历在目。我想,这种对整体设计流程的把握应该是以后走上工作岗位所必需的技能,而这种技能却只能通过自己的亲身实践才能获得。这也是为什么我认为机械设计大作业这种教学实践模式值得推广的原因。毕业设计是我在大学生涯完成的最后一项内容,此时此刻,我感觉自己有很多想要说的话,有很多需要感谢的人。首先感谢指导老师李波和唐宇老师给予的支持与指导,但由于工作的原因和条件的限制,我在外面所做的毕业设计并不完善。自从回校之后,向老师们请教和指导,他们都在百忙之中给予了我悉心的指导和帮助。师生之情无法言表,在此,谨向恩师们深表谢意!也许,我的学生生涯从此就会结束,但是学习的道路却还将持续下去,未来的人生路途中难免会遇到各种各样的困难和挫折,使我始终能够勇敢的迎接新的挑战。参考文献1;冷冲压技术 翁其金主编 北京机械工业出版社 2000.11 2;公差配合与技术测量 薛彦成主编 北京机械工业出版社1999.103;机械制图 李澄 闻百桥 吴天生主编 北京高等教育出版社2003.84;模具设计与制造简明手册 冯炳尧 韩泰来 蒋文森 主编 上海科学技术出版社 1998(第二版)5;模具技术标准应用 全国模具标准技术委员会秘书处四川省模具工业协会印 1992.825Journal of Materials Processing Technology 151 (2004) 237241 Recent developments in sheet hydroforming technology S.H. Zhang a, , Z.R. Wang b ,Y.Xu a , Z.T. Wang a , L.X. Zhou a a Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China b School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China Abstract In this paper, recent developments in sheet hydroforming technology are summarized, several key technical problems to be solved for the development of sheet hydroforming technology are analyzed, and varied sheet hydroforming technologies are discussed. Compound deformation by drawing and bulging is the main direction for the development of sheet hydroforming technology, in which it is advantageous to increase the feeding of materials, and the ratio of drawing deformation (drawing in of the blank flange) to bulging, enabling the forming limit of a sheet blank to be increased. It is also advantageous to increase the local deformation capacity for sheet hydroforming, to increase the range of application of the process. Press capacity is one of the important factors restraining the range of applications. As one of the flexible forming technologies that is still under development, it has much potential for innovative applications. Its applications have been increasing remarkably, recently in automotive companies. A breakthrough in the technology will be obtained by the development of novel equipment. A new sheet hydroforming technology using a movable die is proposed in this paper, which has been developed recently by the authors. 2004 Elsevier B.V. All rights reserved. Keywords: Sheet hydroforming; Drawing in; Bulging; Flexible forming; Forming limit 1. Introduction Compared with conventional deep drawing, sheet hydro- forming technology possesses many remarkable advantages, such as a higher drawing ratio, better surface quality, less springback, better dimensional freezing and the capability of forming complicated-shaped sheet metal parts. For exam- ple a multi-pass forming process may be decreased to one pass for the forming parabolic parts. Sheet hydroforming technology has been applied to industries for the forming of automotive panels and aircraft skins 1. It is a soft-tool forming technology and as the development of this technol- ogy is imperfect compared with other rigid forming tech- nologies, there are more extensive demands and space for it to be improved with the development of modern industry. There are many demands for hydrofoming technology for use with some new materials, such as forming of magnesium alloy sheets, composite material sheets and sandwich sheets. Some new hydroforming processes have entered this area, such as viscous pressure forming technology, warm sheet hydroforming, the hydroforming of sheet metal pairs and the hydroforming of tailor-welded blanks. Through long-term Corresponding author. Tel.: +86-24-8397-8266/8721; fax: +86-24-2390-6831. E-mail address: (S.H. Zhang). investigation by the AP namely, the compound deformation of bulging and drawing due to the draw-in of blank flange area (blank feeding of the blank flange area), which compensates the materials for the stretch of the bulging area and avoids excessive thinning resulting from the increase of the blank area, thus assuring material strength and rigidity in the bulging area. It is very diffi- cult to realize the uniform distribution of thinning, the large local deformation of sheet the metal and the increasing of the forming limit of the blank without blank feeding and supplementation. Thus the advantages for the hydroforming of complicated-shaped parts from sheet cannot be revealed fully, although the breakthrough for tube hydroforming has been realized. A tubular component can be hydroformed if dealing with a high-pressure forming process with the simul- taneous feeding of the tube end 3, which increases the tube area and thus reduces little thinning. The requirements for the pressure of the tool in tube hydroforming are small. The internal pressure for the tube is closed and self-restrained, and the closing force involved is small. The material feeding of the tube end can be enforced without difficulty for this technology, compared with the difficulties of the feeding in of the material in hydroforming. As in tube hydroforming, a closing force is required for sheet hydroforming, but a difficulty is that the closing force for sheet hydroforming is far greater than that in tube hydro- forming, and requires a high press tonnage: this is an impor- tant factor restraining the application of sheet hydroforming. The closing pressure can be supplied by a hydraulic press, but the pressure for sheet hydroforming is no limits and not self-restrained. 2.1. Hydroforming with a rubber diaphragm A rubber membrane was employed as the diaphragm of the hydraulic chamber and the blankholder in the early form of sheet hydroforming. This process has been applied to small batch production of automotive panels and aircraft skins (Fig. 1). There are many advantages for this process: better surface quality and the forming of more complicated workpieces. It is suitable for small batch production. How- ever, it also has some disadvantages, such as low process efficiency and the requirement of heavy presses. In addition, it is easy to destroy the rubber membrane and difficult to control wrinkling. 2.2. The hydromechanical deep drawing process and the hydro-rim deep drawing process The hydromechanical deep drawing process has been de- veloped on the basis of rubber membrane hydroforming (Fig. 2(a). The pressure can be produced by the downwards movement of the punch into the fluid chamber, or supplied by a hydraulic system, because a rubber membrane is not used. Thus, it is very easy to obtain hydraulic pressure. The tool device is similar to a conventional tool. All these param- eters lead to high efficiency. The shape of the workpieces may be very complicated, and the drawing ratio may be in- creased, from 1.8 to 2.7, compared with that for conven- tional drawing processes. There are many applications for this process 1315. More local deformation and forming of complicated parts are realized by using this process. Forced feeding is difficult to practice in current sheet hy- droforming processes. To some extent, the radial hydrome- S.H. Zhang et al. / Journal of Materials Processing Technology 151 (2004) 237241 239 Fig. 1. Sheet hydroforming with a rubber membrane: (a) the process; (b) a hydroformed workpiece. chanical deep drawing (hydro-rim) process can realize some forced radial feeding (Fig. 2(b), which can significantly in- crease the forming limit of the sheet metal. According to the research results in 2, the drawing ratio can be increased, from 2.6 to 3.2, compared with that for the common hy- dromechanical deep drawing process. 2.3. Hydroforming of sheet metal pairs A special case is the hydroforming of welded-closing sheet metal pairs (Fig. 3(a). The hydroforming technology of sheet metal pairs was developed by Kleiner et al at. Dort- mund University in the early 1990s 46. In the first scheme the periphery of the sheet metal can be welded using laser welding. Then a liquid medium can be filled between the blanks, and pressurization can be effected by a hydraulic sys- tem. Plastic deformation starts in the blank under the pres- sure and then further deformation occurs sequentially in the zone contacting with the die. However, it is very difficult to realize radial feeding using this method, as it is essentially a pure bulging deformation. The advantage is that the pres- sure is a kind of self-restraining pressure. There is a low re- quirement for the closing force. A stainless steel automotive model was formed with the new press of 100,000 kN with hydroforming technology. To some extent, this technology is similar to tube hydroforming, however, it is very difficult to realize the radial feeding of the blank. Fig. 2. Showing: (a) hydromechanical deep drawing; (b) hydro-rim deep drawing. Another variation was proposed by Dortmund University (Fig. 3(b). The principle is that the tool system is made up of an upper and lower die and an intermediate plate. The intermediate plate can be applied on its own or together with the upper and lower blank, for hydroforming. The pressure pipeline may be connected or disconnected. Generally, the shape of the upper and lower workpieces is symmetrical when the pressure pipeline is connected, whilst the shapes of the upper and lower workpieces are independent when the pressure pipeline is not connected: infact, they may deform separately. This tool is for the realization of the compound deformation of drawing and bulging. 2.4. The compound deformation of drawing and bulging Sheet hydroforming with compound drawing and bulging has been investigated for many years. Since the early 1980s, the theory of hydroforming with draw-in has been studied by Shang at Singapore National University 7. He studied the reasonable match of draw-in and bulging, but it is still in the research stage and has not been applied. 2.5. The dieless integral hydro-bulge forming (IHBF) of spherical shells Another special case is the integral hydro-bulge forming (IHBF) of spherical shells. IHBF is a new dieless forming 240 S.H. Zhang et al. / Journal of Materials Processing Technology 151 (2004) 237241 Fig. 3. The hydroforming of sheet metal pairs with an intermediate plate. technology for sphere-inner-scribing polyhedral shell, that means, all the side inter-sections of the polyhedral shell sides are on the sphere; which was invented by Wang 8 at Harbin Institute of Technology in 1985. It realized the dieless IHBF of flat sheets. In fact, this technology is a pure bulging process as it is impossible to obtain the supplementation of materials. Moreover, it is a non-uniform bulging forming. The hydroforming of single curvature shells and the dieless IHBF of double spherical vessels, oblate spheroid shells, ellipsoidal shells and pairs of pressure vessel heads were developed later, which resulted in the full development of the dieless IHBF technology and secured wide applications. 3. A new sheet hydroforming technology: hydroforming with a movable die A sheet hydroforming technology with a movable female die was proposed by authors in 2001 (see Fig. 4) 11,12. Some hydroformed workpieces of stainless steel and magne- sium alloys are shown in Fig. 5. For sheet hydroforming with a movable die, a combined die is used, which consists of a fixed part and a movable part. As the technology can realize the compound deformation of drawing and bulging, it is suit- able for forming complicated-shaped parts and low-plasticity difficult-to-form materials. That part of the blank in the flange area is drawn in during the process, which may real- ize the compound deformation of deep drawing and bulging. Fig. 5. Some hydroformed workpieces of stainless steel and magnesium alloy. Blankholder plate Movable die Combination die Bolster plate O-ring sealing Blank Dies Fig. 4. Schematic of the new set-up for sheet hydroforming using a movable die. The movable die component keeps in touch with the blank during the early stage. Plastic deformation and then defor- mation of the blank in the die-contacting area take place. The movable die remains in contact with the blank under the friction force, which makes the deformation area spread to the non-contacting area. Preliminary research shows that the thinning of the sheet metal can be alleviated remark- ably if this innovative process is adopted 12 (see Fig. 6). The forming limit of the sheet metal is increased. This pro- cess is suitable for the forming of complicated-shaped parts such as aluminum alloy sheets, as well as low-plasticity and light-weight materials such as aluminum lithium alloy and magnesium alloys. S.H. Zhang et al. / Journal of Materials Processing Technology 151 (2004) 237241 241 Fig. 6. Comparison of the thinning ratio between hydroforming with and without a movable die. It is difficult for the tool to be damaged or worn because of the use of hydraulic pressure, so the tool life is improved. Moreover, it is very easy to modify the product because the blankholder has versatility and the punch is not required to be changed: it is only required to change the die for the form- ing of different parts. It can be shown that this process has many advantages over conventional processes: it makes the dies contact well, which results in better shape, dimensional accuracy, less springback and higher precision, remarkably lower tools cost and obviously shorter production periods for small batch production. This process is especially suit- able for the production of large-scale sheet metal parts with complicated shape, varied size and of small batch. It makes the production of complicated shape parts simple and flex- ible and realizes the quick production of workpieces. It is especially suitable for the development of new products in the aerospace industry and prototypes in the automotive in- dustry. If the deformation methods of conventional tools are adopted, because the production batch is not great, the de- sign cycle is long and the manufacturing cost is high, whilst if the presently described process is adopted, the cost for the tool will be decreased and the production periods and development cycle will be shortened. It is expected to apply this technology to many other area of manufacture, such as the production of prototype workpieces, which may save the cost of development, shorten the development cycle for the development of new models and improve competitive power for the business. 4. Conclusions In this paper, recent developments of sheet hydroforming technology are discussed systematically. With the realization of the compound deformation of drawing and bulging for further development of sheet hydroforming, more draw-in of blank flange (drawing deformation) and more capacity of local deformation, can be achieved. The forming limit of sheet metal can be significantly increased, and a wider range of part shape can be formed. Moreover, the multi-pass form- ing process for conventional complicated sheet parts can be decreased to one or two passes. Thus higher efficiency and lower costs can be achieved, which compensates for the low efficiency of the single pass procedure of hydroforming. The pre-requisite to the application for this process is a large tonnage for the equipment and high automation. The com- pound deformation of drawing and bulging can be realized if hydroforming with movable dies is adopted. Moreover, the distribution of wall thickness can be controlled. Thin- ning can be decreased and the forming limit of sheet metal can be increased. There are wide prospects for this technol- ogy, and the process can meet the developing direction of production requirements. References 1 S.H. Zhang, Developments in hydroforming, J. Mater. Process. Tech- nol. 91 (1991) 236244. 2 S.H. Zhang, J. 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